Under the skimmer basket there's a white cover, with a valve on one side, that covers two suction holes--one hole is covered by the white thing, and the other hole is exposed, but there's a slide plate on a screw that you can use to cover it. What is the white cover thing with the valve on it (and the slide plate) called?
And what is the purpose of the slide plate? When would I use that?
And what is the purpose of the slide plate? When would I use that?